Technical Field
The present invention relates to energy storage systems, and more particularly to hybrid ultra capacitor-battery storage systems and power management systems.
Description of the Related Art
The energy storage system has been recognized as an effective solution for counteracting the challenges when more and more renewable energy resources are integrated into power grid. Different energy storage technologies have different characteristics, e.g. energy/power density, cycle life, costs, efficiency, etc. For different applications, different aspects of storage system are required. For example, for the compensation of the intermittency of the renewable energy resources, energy storage with high energy density is mainly required. For the system experiencing high power transients, energy storage with high power density and fast dynamics is required. For some micro-grid applications, they have a high requirement on the energy storage system from all the aspects of time-scale, energy-scale and power scale. If a single-type energy storage system is chosen, it will be oversized in some aspects to take care of its weak points, e.g., the battery has to be oversized to respond to high power demand, while the ultra-capacitor has to be oversized to supply a sustainable power support. The application of hybrid energy storage systems can be unavoidable, where various types of storage elements are operated in a complement way to overcome their disadvantages. What is needed is a power management system that can provide for optimal utilization of the energy storage components.